1. Field of the Invention
The present invention concerns the management of paging listening intervals and more particularly, the management of such intervals to improve the efficiency of mobile stations.
2. Description of the Related Art
The idle mode operation in the current specification for IEEE 802.16e defines periodic paging listening intervals that mobile subscriber stations (MSS) tune to in order to receive a series of broadcast paging messages from a base station (BS). Additionally, the BS may assign a number of MSSs to a particular paging group—depending on the functionality and/or desire of the MSSs—that has a predetermined paging cycle. The duration of a paging cycle may vary, with a shorter paging cycle typically reserved for groups of MSSs with time-sensitive applications, such as push-to-talk (PTT) (i.e., dispatch), which may lead to a paging cycle as short as 300 milliseconds (ms). Each listening interval defines the beginning of a paging cycle, and the listening intervals are comprised of one or more frames, the length of which some entities have set at 5 ms.
The 802.16e specification requires the BS to broadcast paging messages during the listening interval, and these paging messages contain information that will be processed by the MSSs receiving it to enable the MSSs to carry out their relevant applications. The standard also requires the MSSs to process every frame of the listening interval, even if an MSS is not being paged. Moreover, certain entities or companies also call for a neighbor advertisement message and/or other broadcast messages to be selectively inserted at the end of a listening interval. The neighbor advertisement message, which contains information about neighboring BSs, allows the MSS to gather data on neighboring BSs for a prompt handover to a neighboring BS when it becomes necessary to do so. To prevent the BS from being overwhelmed by the transmission of the neighbor advertisement messages, however, these messages are inserted only after selected listening intervals. That is, certain listening intervals may not have a neighbor advertisement message positioned at the end of the interval.
During a listening interval, the MSS will process each of the incoming paging messages and will continue to stay awake for the duration of the listening interval so long as it does not detect a paging message designated for its receipt. The MSS will also process the frame after the interval to see if a neighbor advertisement message is present. This process is extremely inefficient because none of the paging messages may be designated for the MS receiving them. Even worse, the MS may continue to stay awake for a neighbor advertisement message that may not be present at the end of the listening interval. The impact on standby battery life is also exacerbated if the paging cycle is short, such as for a group of dispatch MSSs, because the MSS is constantly waking up to listen in the listening interval and the portion of the cycle that may or may not contain the neighbor advertisement message.